$ sudo apt-get update
$ sudo apt-get install freeradius-postgresql 

freeradius-postgresql is installed in your system.

Make ensure the freeradius-postgresql package were installed using the commands given below,

$ sudo dpkg-query -l | grep freeradius-postgresql *

You will get with freeradius-postgresql package name, version, architecture and description in a table

freeradius-postgresql package basic information: